1

Building exterior wall coatings have decorative and protective effects on buildings. Compared with traditional exterior wall decorative materials such as exterior wall tiles and mosaics, it has the characteristics of energy saving, environmental protection, rich colors and easy updating. Therefore, it has developed rapidly in China in recent years, and many provincial and municipal governments have issued relevant documents to restrict or eliminate the use of exterior wall tiles. It is undoubtedly good news for architectural coatings industry to promote architectural exterior wall coatings. A few years ago, imported latex paint not only impacted the domestic market, but also stimulated consumption, which promoted the improvement of product quality of domestic enterprises, thus promoting the development of architectural coatings in China. With the rapid development of building exterior wall coatings, some inferior products enter the market, which leads to quality problems of exterior wall coatings. If such problems are not eliminated, the development of exterior wall coatings will be greatly limited. The competent construction department and quality supervision department are required to strengthen quality control. While production enterprises strive to improve product quality, construction enterprises should also organize construction scientifically and reasonably, strengthen quality management and ensure painting quality.

At present, there is no national unified special construction specification and acceptance standard for building exterior wall coating construction. Only in the industry standard (JGJ. 73-9 1) Code for Construction and Acceptance of Building Decoration Engineering puts forward specifications and requirements for exterior wall painting, but it has not been implemented in actual projects. With the development of production and application technology of architectural coatings, some contents in the specification have not met the current requirements. Shanghai, Jiangsu, Fujian and other regions have revised the local standard price specification for construction and acceptance of wall coatings, but it has not been strictly implemented in the actual project construction management and acceptance, and the construction quality is difficult to guarantee. Architectural painting in developed countries is a specialized industry. The construction unit must have the construction qualification, and the construction personnel must hold the post certificate. At the same time, there are strict and feasible management measures and acceptance standards for construction quality and safety. In order to make the building exterior wall coating industry develop healthily for a long time, it is urgent to strengthen the scientific management of building exterior wall coating construction.

2. The basic requirements and treatment of building exterior wall painting

2. 1 Adequate curing period

The surface of new cement mortar concrete must be maintained for a reasonable period of time to make it "spit alkali" and fully dry. The water content is less than 10% and the PH value is less than 10 before construction. But it is not convenient to measure the moisture content and pH value of the wall. Theoretically, under the condition of temperature of 25 degrees and relative humidity of 65%, the cement mortar wall should be dried more than 2 1d, but in different seasons, according to experience, it usually takes more than 2 weeks in summer and 4 weeks in winter. At present, some high-rise buildings often dismantle the scaffolding and maintain it for more than two months after the external wall painting is completed, and then use the hanging basket for external wall painting construction, which not only reduces the moisture content and pH value, but also can timely deal with the defects such as wall shrinkage and cracking, which greatly ensures the quality of external wall painting. However, some multi-storey buildings often can't guarantee enough maintenance period due to the construction period and scaffolding problems, leaving hidden dangers for exterior wall painting.

1: First of all, sufficient curing time is difficult to achieve. Now the time limit for a project is not long, and the time limit for the exterior wall paint is even shorter. It is difficult to ensure that the requirements of natural conservation period are fully met, so it is impossible to completely "spit alkali".

2. Different coatings have different requirements for the bottom surface. Solvent-based coatings require water content of the bottom surface to be less than 8%, water-soluble coatings require water content of the bottom surface to be less than 10%, and if the bottom surface is made of wood, it can be less than 12%.

2.2 The underlying treatment shall be qualified.

The bottom surface should be dry, solid and firm, and there should be no sand and cracks. Loose and other defects. The primer for exterior wall painting can be divided into ordinary, intermediate and advanced plastering primer or concrete primer according to painting requirements. Before building exterior wall coating construction, plastering and concrete bottom layer must be accepted. Without acceptance or unqualified acceptance of metope can't paint. If there are sand, cracks and looseness on the wall surface, the civil engineering unit shall be required to handle it. Loose layer should be removed, cracks, missing edges and corners should be repaired, and construction can only be started after acceptance.

It should be said that among the wall quality defects, hollowing is the biggest threat to paint construction. When the paint starts construction, it means that the wall is recognized. Many projects have short construction period and inadequate technology, which leaves hidden dangers for the quality of walls. Therefore, before the paint enters the construction site, it is necessary to cooperate with the supervisor and the civil contractor to strictly check and accept the wall surface. If there is no such acceptance, it will cause a lot of trouble for future construction.

2.3 bottom surface cleaning

The bottom surface must be clean and free of dirt, frost, oil stain, release agent and other pollutants. If the above accessories are found, shovel, wire brush and sandpaper should be used. Detergent, etc. It should be removed, then rinsed with clean water and dried before painting. Construction should be carried out as soon as possible after wall treatment to avoid re-pollution.

The protection of windows, especially the popular large-area floor-to-ceiling windows made of plastic steel. Once the polluted putty or paint on the plastic steel is extremely difficult to clean, and most of the engineering plastic steel window frames are completed before painting, in line with the principle of "whoever builds will protect", the paint builders must be careful to protect the plastic steel, otherwise it will be very troublesome to clean up. The best way is to negotiate mutually beneficial conditions with plastic steel production units, such as letting them repair plastic windows and apply sealant with hanging baskets for free.

2.4 Exterior wall framing

Exterior walls are painted with straight frame lines, and there are many forms of frame strips. In the past, battens were often embedded in plastering mortar. After painting construction, remove this article first, and then tick off the seam with dark paint. In recent years, a large number of plastic grid strips have been used, with various forms and good results. However, attention should be paid to protect the grid bars during paint construction, and the grid bars should not be polluted by paint. Whether it is wood or plastic, the material is required to be hard and straight, and it is not easy to deform.

2.5 treatment of plastering layer

Exterior wall painting is not suitable for mass scraping putty. It is suggested that the plastering layer should be brushed carefully before applying primer and topcoat. If it is really necessary to scrape putty, it is recommended to use polymer cement putty. Ordinary low-strength interior wall putty, including 80 1 glue and cement putty, cannot be used, and the putty layer should not be too thick. It is required that the bottom layer of the wall should not be too rough, which will affect the decoration quality, but it should not be too smooth, which will reduce the adhesion of the paint.

3 construction scheme and construction method

3. 1 Thin-layer exterior wall coating construction

Include synthetic resin emulsion exterior wall coatings and solvent-based exterior wall coatings. Synthetic resin emulsion exterior wall coating (latex paint) has high, medium and low-grade products, which are suitable for different levels of consumers. Solvent-based exterior wall coatings belong to high-grade exterior wall coatings, which are used in painting projects with high requirements.

◆ Thin-layer exterior wall coating is especially suitable for fine brushing walls. If you need to blow putty in batches, you should choose polymer cement putty, not too thick.

◆ Generally, primary coating and secondary surface coating are adopted. According to the requirements of engineering quality, the number of surface painting can be increased appropriately.

◆ The function of primer: seal the alkalinity of the wall, improve the adhesion between the top coat and the wall, avoid absorbing a lot of paint because the wall is too dry, ensure the same amount of material absorption, and increase the strength of the underlying material. However, the function of primer is limited. Although the primer is used, the pH value and moisture content of the bottom layer must meet the requirements before construction.

◆ Construction method: roller coating, brush coating, gas spraying and airless spraying can be used.

Selection of color: Fading of exterior wall paint is a common problem. High-quality exterior wall coatings fade slowly, which does not mean that they will never fade. Therefore, it is generally recommended to choose a darker or darker color for exterior wall coatings. On the one hand, buildings look calm and generous, on the other hand, darker colors are generally made of inorganic pigments, which have better weather resistance than organic pigments, so they fade slowly. In addition, the same building should use the same batch of paint to ensure the same color.

◆ The painting construction of the building should be carried out from top to bottom, and each painting should be bounded by the dividing line, the junction of the Yin and Yang corners of the wall or the downpipe.

◆ The construction interval (recoating time) shall be carried out in strict accordance with the product instructions.

◆ After painting, stir thoroughly and evenly. If the axis is too large, thinner can be added according to the instructions (latex paint is usually added with water) to adjust the construction performance. Pay attention to the requirements, especially latex paint, do not add too much water, otherwise it will make the dried coating difficult to form a film, reducing the gloss, durability and hiding power of the coating.

◆ Influence of temperature and humidity. The minimum temperature for painting construction is usually specified in the paint description. Latex paint requires the highest construction temperature. If the construction is carried out below a certain temperature, it will lead to poor film formation. There is also a misunderstanding here: some users think that the temperature of high-grade latex paint can be lower during construction, but in fact it is just the opposite. Because middle and high-grade latex paints are generally prepared with emulsions with high glass transition temperature and high emulsion ratio, even if a large number of film-forming additives are added, higher film-forming temperature, that is, construction temperature, is still needed.

In addition, in southern China, humidity often affects the construction quality, especially solvent-based exterior wall coatings. When the humidity is more than 85%, it is generally not suitable for construction, because when the humidity is too high, the coating dries slowly, which not only affects the adhesion between the coating and the wall, but also makes the wall frost easily. Therefore, when the air humidity is saturated, such as foggy days, painting construction cannot be carried out, but after heavy rain, construction can only be carried out after the wall is dried.

3.2 Construction of Multilayer Coatings

Multi-layer exterior wall coating is also called concave-convex pattern coating or embossed plastic spraying coating. There is a concept here that needs to be changed: in the past, it was emphasized that when multilayer coatings were constructed, the particles should be large and the concave-convex feeling should be strong. However, due to the current environmental pollution and other reasons, the exterior wall coating with fine and uniform particles and slight concave-convex feeling is often popular now, also called orange peel exterior wall coating.

◆ Multi-layer coating does not require the bottom layer to be very flat, and it is more reasonable to choose multi-layer coating for rough wall painting. For the application of obvious defects such as missing edges and falling corners, polymer cement putty can be used to repair them before painting.

Need to brush primer, because primer can not only seal the alkalinity of the wall, adjust the permeability of the bottom layer, but also increase the adhesion of the main coating, so it is not allowed to brush or not.

◆ Construction of main coating: The main coating is also called aggregate. If it belongs to the reaction curing type, it should be prepared as needed, and it should not be stored for a long time, and the ingredients should be supervised by special personnel to ensure the accuracy of the ingredients. Mechanical spraying is generally used in the construction of main coating paint, and a trial spraying is required before construction. At the same time, the hardness of paint, the type of spray gun, the diameter of nozzle, the muzzle air pressure, the distance and angle between spray gun and wall surface should be adjusted appropriately. Should spray template first, after inspection qualified rear can large-scale construction.

◆ The separation line of Yin and Yang angles should be blocked, and the walking route of the spray gun can be up and down or left and right, and the uneven place should be sprayed again to ensure uniformity. After the main coating is sprayed, it can be rolled with plastic roller or rubber roller dipped in kerosene and other solvents as needed, and there should be no obvious joint marks at the joints of each roller.

◆ The orange peel-like exterior wall coating project is also constructed by thick thixotropic latex paint, which is similar to decorative mortar. Choose different kinds of rollers to create different shapes. The technique of this kind of paint in construction is very important. For example, the amount of dipping and the amount of force each time will affect the shape of the pattern, so the construction personnel should try the roller repeatedly and master the essentials before carrying out large-scale construction.

◆ Topcoat: Generally, the surface of the main coating is covered with two layers of paint, and the topcoat can be solvent-based exterior wall coating or synthetic resin emulsion exterior wall coating latex paint). The construction of overlay coating is the same as that of thin-layer exterior wall coating.

3.3 Construction of exterior wall coating of colored sand wall

Painted sand wall exterior wall coating is also called exterior wall sandblasting. This kind of coating used to be the decorative coatings for the exterior walls of most residential quarters, but its application has been limited in recent years due to its poor stain resistance. On this basis, two new types of exterior wall decorative coatings-pearlescent paint and real stone paint were developed. The so-called pearlescent paint refers to the coating of solvent-based exterior wall paint or glossy latex paint on the sandblasted exterior wall surface, so that the coating surface forms a pearl-like luster effect, hence the name "pearlescent paint". Real stone paint is a high-grade external wall made of natural stone powder particles with different particle sizes, and then coated with solvent-based finish varnish.

◆ If the bottom surface has defects such as missing edges, corners, holes, cracks and pits, it should be repaired with polymer putty.

◆ In order to reduce the water absorption of the bottom layer and enhance the adhesion, a layer of sealing primer can be coated on the bottom layer. Real stone paint is a natural stone with poor hiding power, so it is necessary to prepare a sealing primer with similar color to effectively ensure the decorative effect of real stone paint.

◆ Operation of spray gun. The pressure during spraying should be controlled at 0.6~0.8MPa. If the pressure is too low, the discharge is too slow; If the pressure is too great, the rebound will be great. In addition, the vertical distance between the spray bucket and the wall should be about 50 cm. When the spray gun is running, it must be perpendicular to the coating surface and move in a plane parallel to the coating surface. When spraying, the intermediate coating is generally dense and the side surface is sparse, so each line needs to run around 1/3 repeatedly. The running speed of the spray gun should be consistent. If you run too fast, the coating will be thin, the color will be uneven and the hiding power will be poor. If the operation is too slow, it will cause local paint to be too thick or even sag. Real stone paint can be sprayed twice according to the need of decorative effect. Before spraying construction, it should be checked that the scaffold can't be close to the wall, otherwise it is easy to form obvious summer-planting on the scaffold, which will affect the painting effect.

◆ Topcoat coating: The surface of pearlescent paint should be coated with high-grade exterior wall coating, and the color can be white or colored, and the color can not be too dark or too light, because it is not like pearlescent color if it is too deep, and it will fade faster if it is too light. The top coat should have a certain luster. Two-component reactive curing topcoat, such as epoxy acrylic varnish or polyurethane acrylic varnish, should be selected as the topcoat of real stone paint, which can improve the stain resistance of the final coating, while the common thermoplastic acrylic varnish has poor stain resistance.

4 case study

Common problems such as temperature, humidity and bottom treatment that should be paid attention to in the construction of exterior wall coatings. The following is an analysis of several cases. (Note: The cases listed below and the problems analyzed are all caused by normal coating performance and improper construction. )

4. 1 Influence of construction temperature

Exterior wall latex paint generally needs to be constructed above 5 degrees Celsius, and a few bright latex paints need to be constructed above 10 degrees Celsius. For example, in winter, although the highest temperature at noon can meet the requirements, due to the low temperature in the morning and evening, if the construction workers do not pay attention to adjusting the construction time in time, some construction walls will have poor film formation. For example, at the beginning of 1996, a residential area in Nanjing chose a factory's bright latex paint for construction. After the construction, it was found that the wall facing north was generally cracked, and the coating was fish-scale-like, which fell off when touched. Finally, the field analysis shows that the coating construction temperature was at the edge of the lowest film-forming temperature at that time, and there was no sunlight on the wall facing north, so the actual coating temperature did not reach the minimum film-forming temperature, resulting in poor film-forming on the wall facing north, which caused the above consequences. In addition, the construction temperature required for paint construction refers to the lowest temperature of the day. If the minimum temperature can't be reached, construction can't be carried out in the morning and evening when the temperature is low.

4.2 the influence of construction humidity

The influence of construction humidity on painting construction is often ignored, but when the humidity is more than 85% or the wall is still wet after rain, exterior wall painting construction cannot be carried out. For example, in February of 1997, Nanjing was foggy continuously and the air humidity was often saturated. When painting in a residential area, the exterior wall was sandblasted. After more than ten days of construction, the wall is still wet, the paint is sagging, and some resin flows down with the fog. After the weather clears up, all the paint on the wall can only be removed and repainted.

4.3 the impact of the underlying processing

In painting construction, there is another problem that is easily overlooked-the treatment of the bottom layer.

The most common way is to use low-strength putty, which affects the quality of the coating and eventually causes the destruction of the whole coating. For example, 1997 When a dormitory building was built in a certain unit, a brand of high-quality exterior wall latex paint was used for exterior wall coating construction. Due to continuous sunny days, the construction is smooth and the coating surface effect is good, which has passed the preliminary acceptance. However, after a heavy rain, a large area of bubbles appeared on the wall, and after the rain stopped, some walls appeared wrinkles. Finally, through field analysis, it is considered that the wall is putty made of cellulose and white powder, which has high strength.

Too thick putty causes the wall to crack and fall off. Generally speaking, it is suggested that when painting exterior walls, it is not advisable to blow putty on a large area. If you really want to blow putty, you should not blow it too thick. This is because the putty layer is easy to crack or even fall off because of different materials and different expansion coefficients. For example, a high-rise building, the external wall painting is not ideal, the surface roughness is poor, and the painting construction unit decided to use the batch putty layer to remedy it. Results After one year, cracks appeared in a large area of the external wall, and the putty layer peeled off locally. It is found that the putty layer is polymer cement putty with sufficient strength, and the main reason for the cracks is that the local putty layer is too thick (more than 1cm thick).

5 concluding remarks

Based on the practical experience of engineering construction management, this paper makes a superficial discussion on the construction of building exterior wall coatings. It can be believed that as long as the building coating production enterprises are stable and improve the product quality, and the construction units organize the construction scientifically and reasonably, the building coating industry will surely develop rapidly and steadily.

Construction scheme of exterior wall latex paint (2)

The field project of farmers' resettlement housing undertaken by our company is in the stage of intense decoration and construction. The putty powder of external wall coating of 5# building ~1# building and 23 # building ~ 25 # building has been used as the base of external steel pipe scaffold, and only the surface coating has not been brushed. In order to catch up with the progress, our construction party considers riding rope at high altitude with exterior wall coating. Rope-sitting construction at high altitude is to hang people to their working positions with hanging ropes and hanging boards. This operation is relatively simple, as long as the workers have good physical fitness and the ropes are firmly connected. General buildings can be constructed in this way, but safety measures must be put in place in this operation, otherwise it will be very dangerous, and all casualties are caused by inadequate safety measures. Therefore, in order to ensure the engineering quality and construction safety, this scheme is formulated.

A, the project post division requirements and responsibilities

1, project manager:

Need to have many years of management experience in aerial work of various external walls, be responsible for the concrete implementation of building external wall coating engineering, and coordinate and solve various problems in construction.

2. On-site supervisor:

It is necessary to have many years of experience in the management and implementation of aerial work in various buildings, and cooperate with the project manager to dispatch and guide on-site personnel.

3. Construction personnel: In order to implement the national safety laws and regulations and ensure the personal safety of operators and the normal operation of equipment, it is stipulated that aerial workers must be male citizens who are 18 -40 years old, have many years of aerial work experience in various buildings, have good personal comprehensive quality, weigh 60 kilograms and have good eyesight, and can only engage in aerial work after passing the physical examination and safety technical training. Anyone suffering from hypertension, heart disease, epilepsy, mental illness and other people who are not suitable for aerial work is prohibited from aerial work. Workers are not allowed to drink alcohol before taking up their posts, and aerial work will be suspended if they have symptoms such as colds.

Second, the safety guarantee of the rope-sitting exterior wall coating construction

1, rope-sitting exterior wall coating construction should be carried out under the condition of ensuring safety. Our company's aerial workers have been trained in aerial work, and they have very rich practical experience and good physical fitness.

2. Under the condition of ensuring safety, the construction of cable-stayed exterior wall coating should ensure the quality, and the two are consistent.

Our company's high-altitude construction team has accumulated rich experience after many campaigns and won unanimous praise from Party A and the supervisor. So far, there is no accident record, and the safety construction has reached 100%.

3. The outer wall putty priming has been completed, and the surface coating operation is not hard, which reduces the hanging rope shaking and increases the safety factor.

Third, the tools used

1. Hanging rope: also known as aerial work rope, with a diameter of 18mm and a tensile force of 240,000 Newton (about two and a half tons in total).

2. Auxiliary rope: also known as safety protection rope, with a diameter of 16mm and a tensile force of 22,000 Newton (about two tons in total).

3. Hanging board: made of Fraxinus mandshurica wood.

4.u-shaped crab clasp: steel

Four kinds of sitting high-altitude hanging boards are assembled. First, choose a fixed place at the top of the building to tie ropes, such as pipes and concrete columns. This place is critical and needs to be tested for impact resistance. The rope should be beaten several times more, and the repeated load test should be foolproof. All corners, edges and eaves of the rope are padded with rubber to prevent friction. Tie a special knot on the U-shaped crab buckle on the sitting suspension board, and bolt a bucket on the side of the board, which contains half a bucket of exterior wall paint. Staff can board the board and start working with the racket brush and roller brush. Because of the special fastening method, the hanging plate will not slip when working. People control the rope and can operate it freely. To put it simply: lift the rope and the hanging board will slide down. Slide as fast as you can until the work is over. An aerial worker can finish the task of painting the external wall of about 200 square meters in one day.

Fourth, the operation process

1. The operator sits at the designated position of the lifting plate and connects all equipment to the upper and lower sides of the lifting plate.

2. Slowly lower the hanger to the first working position.

3, with a brush, roller brush in accordance with the quality requirements of the work position for construction.

4. After the work in one position is finished, slowly adjust to the next position to continue cleaning until the longitudinal position is over, and then move the position horizontally.

5, the whole work process, the roof set personnel to do safety protection, to prevent accidents, floor set security patrol protection personnel, safety supervision should be on-site safety supervision from beginning to end, shall not be absent without leave.

Five, the external wall construction conditions

1. Climatic conditions: the construction of external walls must be carried out in good climatic conditions, and the wind is less than Grade 4, and the operation shall be stopped above Grade 4. So measure the wind before work, especially at high altitude. In addition, rain, snow, fog, poor visibility, high temperature (above 35℃) and low temperature (below 0℃) are not suitable for external wall cleaning.

2. Equipment conditions: the equipment used for external wall construction must be in good working condition. If the hanging plate is hairy and some strands are gradually cracked, a new rope should be replaced immediately.

Six, safety operation procedures

1, work must be carried out in compliance with engineering standards, safety operation specifications and quality standards must be strictly implemented, and the task can be completed on time with good quality and quantity.

2, should abide by the relevant provisions of the project management, civilized construction, shall not affect the work or life of others.

3. We should actively cooperate with the construction management and supervision personnel on the project site to supervise the quality and safety of the project, accept the guidance of the construction management and supervision personnel, and rectify the unqualified projects in time.

4. Before going to work, you must carefully check whether the mechanical equipment, appliances, ropes, seat plates and safety belts are damaged, ensure that the mechanical performance is good, and all kinds of appliances are free from abnormal phenomena, before you can operate at your post.

5. The operating rope and safety rope must be tied separately. Soft objects should be padded along the mouth to prevent the rope from breaking due to wear. The lower end of the rope must touch the ground, and the rope puller should also wear a temporary safety rope.

6. Construction personnel should wear work clothes and safety helmets before taking up their posts. Fasten the safety belt first, then fasten the safety lock (on the safety rope), and then fasten the shackle (on the operating rope). At the same time, the buttons on the board should be fastened and fastened.

7, pay-off, construction director and upstairs care personnel to give command and help.

8. When operating, auxiliary devices should be fastened. In case of falling and injuring people, it is forbidden to laugh and play and carry other irrelevant items.

9, upstairs, ground monitoring personnel should stick to the construction site. Seriously perform their duties. Observe the tightness of operating rope and safety rope, rope winding and stringing at any time, report the problems in time and eliminate them in time.

10, upstairs wardens are not allowed to walk back and forth at the edge of the roof. When necessary, you must fasten your own safety rope first, and then carry out auxiliary work. The ground supervisor is not allowed to read books and newspapers at the construction site, and is not allowed to watch other sites at will. At any time, pedestrians should be stopped from entering dangerous areas and pulling and throwing ropes.

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12, when construction workers want to land, they should first check the facilities on the ground and walls, the positioning of operating ropes and safety ropes, and the amount of pedestrian flow. After being processed and adjusted by the ground monitoring personnel, it can slowly descend until it reaches the ground.

13, adhere to the safety first, civilized construction, to ensure the engineering quality.

14, you are not allowed to take things from the site at will, and you are not allowed to damage various facilities on the site.

15, aerial work personnel and site monitoring personnel must obey the unified command and management of the construction director.

Seven, the end of the operation

1. Put all the lifting ropes and safety ropes away and check them one by one for damage. If the rope is found to be damaged, it should be scrapped immediately.

2, make a good record of work on duty, and signed by the security officer and foreman.